A hydrogen-generation assembly is an assembly that converts one or more feedstocks into a product stream containing hydrogen gas as a majority component. The produced hydrogen gas may be used in a variety of applications. One such application is energy production, such as in electrochemical fuel cells. An electrochemical fuel cell is a device that converts a fuel and an oxidant to electricity, a reaction product, and heat. For example, fuel cells may convert hydrogen and oxygen into water and electrical potential, which also may be referred to as electricity, an electric current, and/or the electrical output of the fuel cell. In such fuel cells, the hydrogen is the fuel, the oxygen is the oxidant, and the water is the reaction product. Fuel cells typically require high purity hydrogen gas to prevent the fuel cells from being damaged during use. The product stream from a hydrogen-generation assembly may contain impurities, illustrative, non-exclusive examples of which include one or more of carbon monoxide, carbon dioxide, methane, unreacted feedstock, and water. Therefore, there is a need in many conventional fuel cell systems to include suitable structure for removing impurities from the product hydrogen stream.
A pressure swing adsorption (PSA) process is an illustrative, non-exclusive example of a mechanism that may be used to remove impurities from an impure hydrogen gas stream by selective adsorption of one or more of the impurities present in the impure hydrogen stream, The adsorbed impurities can be subsequently desorbed and removed from the PSA assembly. PSA is a pressure-driven separation process that utilizes a plurality of adsorbent beds. The beds are cycled through a series of steps, such as one or more pressurization, separation (adsorption), equalization, depressurization (desorption), and/or purge steps to selectively remove impurities from the hydrogen gas and then desorb the impurities.
An energy-producing assembly is a combination of a hydrogen-generation assembly, PSA assembly, fuel cell, and related system components. Energy-producing assemblies are used to produce some form of usable energy, such as electrical or thermal energy. In some applications, there may be a need to take the energy-producing assembly from a dormant state, in which it is not producing energy, to an energy-producing state as quickly as possible. As an illustrative, non-exclusive example, in situations where the energy-producing assembly is used to supply backup power to an energy-consuming device when the primary power source becomes unavailable, reducing the startup time of the energy-producing assembly may be critical to ensuring the continued operation of the energy-consuming device. Reducing the startup time of the energy-producing assembly may include optimizing the startup characteristics and methods for each individual component of the assembly. This disclosure relates to methods for optimizing the startup time of a PSA assembly in such a system, and to hydrogen-producing fuel processing and fuel cell systems containing such a PSA assembly.